Polymodal faulting

time for a new angle on shear failure

David Healy, Thomas G Blenkinsop, Nicholas E. Timms, Philip G Meredith, Thomas M Mitchell, Michele L Cooke

Research output: Contribution to journalArticle

21 Citations (Scopus)
36 Downloads (Pure)

Abstract

Conjugate, or bimodal, fault patterns dominate the geological literature on shear failure. Based on Anderson’s (1905) application of the Mohr-Coulomb failure criterion, these patterns have been interpreted from all tectonic regimes, including normal, strike-slip and thrust (reverse) faulting. However, a fundamental limitation of the Mohr-Coulomb failure criterion – and others that assume faults form parallel to the intermediate principal stress, σ2 – is that only plane strain can result from slip on the conjugate faults. However, deformation in the Earth is widely accepted as being three-dimensional, with truly triaxial stresses (σ1 > σ2 > σ3) and strains. Polymodal faulting, with three or more sets of faults forming and slipping simultaneously, can generate three-dimensional strains from truly triaxial stresses. Laboratory experiments and outcrop studies have verified the occurrence of the polymodal fault patterns in nature. These fault patterns present a fundamental challenge to our understanding of shear failure in rocks (and other materials) and an opportunity to improve our understanding of seismic hazards and fluid flow in the subsurface. In this review, we assess the published evidence, theories and models for polymodal faulting before suggesting ways to produce a truly general and valid failure criterion for triaxial failure.
Original languageEnglish
Pages (from-to)57-71
Number of pages15
JournalJournal of Structural Geology
Volume80
Early online date3 Sep 2015
DOIs
Publication statusPublished - Nov 2015

Fingerprint

faulting
plane strain
seismic hazard
fluid flow
outcrop
thrust
tectonics
rock

Keywords

  • fault
  • pattern
  • quadrimodal
  • conjugate
  • failure

Cite this

Healy, D., Blenkinsop, T. G., Timms, N. E., Meredith, P. G., Mitchell, T. M., & Cooke, M. L. (2015). Polymodal faulting: time for a new angle on shear failure. Journal of Structural Geology, 80, 57-71. https://doi.org/10.1016/j.jsg.2015.08.013

Polymodal faulting : time for a new angle on shear failure. / Healy, David; Blenkinsop, Thomas G; Timms, Nicholas E.; Meredith, Philip G; Mitchell, Thomas M; Cooke, Michele L.

In: Journal of Structural Geology, Vol. 80, 11.2015, p. 57-71.

Research output: Contribution to journalArticle

Healy, D, Blenkinsop, TG, Timms, NE, Meredith, PG, Mitchell, TM & Cooke, ML 2015, 'Polymodal faulting: time for a new angle on shear failure', Journal of Structural Geology, vol. 80, pp. 57-71. https://doi.org/10.1016/j.jsg.2015.08.013
Healy, David ; Blenkinsop, Thomas G ; Timms, Nicholas E. ; Meredith, Philip G ; Mitchell, Thomas M ; Cooke, Michele L. / Polymodal faulting : time for a new angle on shear failure. In: Journal of Structural Geology. 2015 ; Vol. 80. pp. 57-71.
@article{168fcb8162044e0cb3994206258bca89,
title = "Polymodal faulting: time for a new angle on shear failure",
abstract = "Conjugate, or bimodal, fault patterns dominate the geological literature on shear failure. Based on Anderson’s (1905) application of the Mohr-Coulomb failure criterion, these patterns have been interpreted from all tectonic regimes, including normal, strike-slip and thrust (reverse) faulting. However, a fundamental limitation of the Mohr-Coulomb failure criterion – and others that assume faults form parallel to the intermediate principal stress, σ2 – is that only plane strain can result from slip on the conjugate faults. However, deformation in the Earth is widely accepted as being three-dimensional, with truly triaxial stresses (σ1 > σ2 > σ3) and strains. Polymodal faulting, with three or more sets of faults forming and slipping simultaneously, can generate three-dimensional strains from truly triaxial stresses. Laboratory experiments and outcrop studies have verified the occurrence of the polymodal fault patterns in nature. These fault patterns present a fundamental challenge to our understanding of shear failure in rocks (and other materials) and an opportunity to improve our understanding of seismic hazards and fluid flow in the subsurface. In this review, we assess the published evidence, theories and models for polymodal faulting before suggesting ways to produce a truly general and valid failure criterion for triaxial failure.",
keywords = "fault, pattern, quadrimodal, conjugate, failure",
author = "David Healy and Blenkinsop, {Thomas G} and Timms, {Nicholas E.} and Meredith, {Philip G} and Mitchell, {Thomas M} and Cooke, {Michele L}",
note = "Date of acceptance: 30/08/2015 Acknowledgements We thank the Editors of the Journal of Structural Geology for their invitation to write this article, and for their patience while the document was produced. We also thank Ze'ev Reches and Laurel Goodwin for their thoughtful reviews that helped us to refine the key points and forced the lead author to think again about a possible kinematic model for polymodal faulting.",
year = "2015",
month = "11",
doi = "10.1016/j.jsg.2015.08.013",
language = "English",
volume = "80",
pages = "57--71",
journal = "Journal of Structural Geology",
issn = "0191-8141",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Polymodal faulting

T2 - time for a new angle on shear failure

AU - Healy, David

AU - Blenkinsop, Thomas G

AU - Timms, Nicholas E.

AU - Meredith, Philip G

AU - Mitchell, Thomas M

AU - Cooke, Michele L

N1 - Date of acceptance: 30/08/2015 Acknowledgements We thank the Editors of the Journal of Structural Geology for their invitation to write this article, and for their patience while the document was produced. We also thank Ze'ev Reches and Laurel Goodwin for their thoughtful reviews that helped us to refine the key points and forced the lead author to think again about a possible kinematic model for polymodal faulting.

PY - 2015/11

Y1 - 2015/11

N2 - Conjugate, or bimodal, fault patterns dominate the geological literature on shear failure. Based on Anderson’s (1905) application of the Mohr-Coulomb failure criterion, these patterns have been interpreted from all tectonic regimes, including normal, strike-slip and thrust (reverse) faulting. However, a fundamental limitation of the Mohr-Coulomb failure criterion – and others that assume faults form parallel to the intermediate principal stress, σ2 – is that only plane strain can result from slip on the conjugate faults. However, deformation in the Earth is widely accepted as being three-dimensional, with truly triaxial stresses (σ1 > σ2 > σ3) and strains. Polymodal faulting, with three or more sets of faults forming and slipping simultaneously, can generate three-dimensional strains from truly triaxial stresses. Laboratory experiments and outcrop studies have verified the occurrence of the polymodal fault patterns in nature. These fault patterns present a fundamental challenge to our understanding of shear failure in rocks (and other materials) and an opportunity to improve our understanding of seismic hazards and fluid flow in the subsurface. In this review, we assess the published evidence, theories and models for polymodal faulting before suggesting ways to produce a truly general and valid failure criterion for triaxial failure.

AB - Conjugate, or bimodal, fault patterns dominate the geological literature on shear failure. Based on Anderson’s (1905) application of the Mohr-Coulomb failure criterion, these patterns have been interpreted from all tectonic regimes, including normal, strike-slip and thrust (reverse) faulting. However, a fundamental limitation of the Mohr-Coulomb failure criterion – and others that assume faults form parallel to the intermediate principal stress, σ2 – is that only plane strain can result from slip on the conjugate faults. However, deformation in the Earth is widely accepted as being three-dimensional, with truly triaxial stresses (σ1 > σ2 > σ3) and strains. Polymodal faulting, with three or more sets of faults forming and slipping simultaneously, can generate three-dimensional strains from truly triaxial stresses. Laboratory experiments and outcrop studies have verified the occurrence of the polymodal fault patterns in nature. These fault patterns present a fundamental challenge to our understanding of shear failure in rocks (and other materials) and an opportunity to improve our understanding of seismic hazards and fluid flow in the subsurface. In this review, we assess the published evidence, theories and models for polymodal faulting before suggesting ways to produce a truly general and valid failure criterion for triaxial failure.

KW - fault

KW - pattern

KW - quadrimodal

KW - conjugate

KW - failure

U2 - 10.1016/j.jsg.2015.08.013

DO - 10.1016/j.jsg.2015.08.013

M3 - Article

VL - 80

SP - 57

EP - 71

JO - Journal of Structural Geology

JF - Journal of Structural Geology

SN - 0191-8141

ER -